Tannin complexation with metal ions and its implication on human health, environment and industry: An overview

• Published in: International journal of biological macromolecules 2023-12, Vol.253, p.127485-127485, Article 127485
• Main Authors: Zhang, Liangliang, Guan, Qinhao, Jiang, Jianchun, Khan, Mohd Shahnawaz
• Format: Article
• Language: English
• Subjects: antioxidants; chemical structure; class; desulfurization; dyeing; gallic acid; human health; industry; leather; Metal-binding; oils; Polyphenol; proanthocyanidins; renewable resources; secondary metabolites; Stability constants; Stoichiometry; Tannins; water treatment; wood
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2023.127485

Tannins, also known as plant polyphenols (PPs), are secondary metabolites widely existing in higher plants and are a kind of natural renewable resource with wide distribution, variety and quantity. Tannin has become an important class of fine chemicals due to the easily modified molecular structure and the properties of antibacterial and antioxidant, combining with protein and complexing with metal ion. Besides being used for tanning leather, tannins are also widely used in wood adhesive, concrete water-reducing agents, oil drilling fluid viscosity-reducing agents, pharmaceutical, mineral processing, water treatment, gas desulfurization, metal anticorrosion, wood anticorrosion, printing and dyeing, liquor clarification, oil antioxidant, daily chemical products and other products preparation. There are two groups of tannins: condensed tannins (CTs) (flavonoid-derived proanthocyanidins) and hydrolysable tannins (HTs) (gallic acid ester-derived). Tannins can form complexes with metals through the ortho-dihydroxyphenolic group(s), especially with transition metals. The structure-activity relationships, stoichiometry, and origin of the insolubility of which were emphasized. Furthermore, this paper proposed an in-depth discussion of the associations of tannins-metal complexes in human health, environment and industries. [Display omitted] •Studies on complexation of tannins with metal ions were reviewed.•Stoichiometry and origin of the insolubility of complex were emphasized.•Implication of tannins-metal complexes in human health was discussed.